The present invention relates to material collection systems using gas flow induced by a vacuum source to convey non-gaseous material to be collected.
More particularly the invention relates to collection systems particularly adapted to suctioning of body fluids by creating a negative gauge pressure in a collection vessel and ingesting non-gaseous fluid through a conduit in flow communication with the vessel.
In a typical hospital, several operating rooms have body fluid collection systems connected to the same central vacuum source. When prior art systems expose an inlet conduit to the atmosphere, they unnecessarily consume additional energy in driving the pump section of the vacuum source by ingesting large quantities of air. The pumping of such large quantities of air through the prior art systems is, in addition to being wasteful of energy, excessively noisy. Also, the level of vacum may become dangerously low.
The present invention reduces the flow of gas through the system upon exposure of an inlet conduit to the atmosphere and thus reduces energy usage and noise. This can be accomplished while maintaining the vacuum level at a desirable level in systems including a plurality of inlet conduits, without compromising the maximum attainable vacuum developed by such a system and without significant reductions in the final rate of collection of non-gaseous fluids.
The present invention is particularly well suited for use in medical applications where the non-gaseous fluids to be collected are body fluids generated by surgical and non surgical intrusion into the body. In such medical applications, the collection system should initially exert gentle suction on the fluids available for collection the body which thereby minimizes grabing of adjacent tissue or lung collapse. The system should, however, provide sufficient differential pressure between the collection vessel and the inlet conduit so that relatively viscous materials can be ingested into the inlet conduit tip and subsequently as the vacuum increases into the collection vessel.
A prior art system is described in U.S. Pat. No. 3,812,855 where an ophthalmic surgical device is disclosed having fluid dispensing and collection means. The device of this reference uses a variable flow restricting element to control the flow rate of fluid either delivered or ingested by a surgical probe. The extraction or delivery of fluid to the interior of the eye is, of course, a critical manipulation of material and the variation of fluid amounts and their flow rates of extraction and insertion must be varied exactly. This prior art reference controls the flow rate of fluid by acting on the fluid itself. By contrast the present invention controls the rate of extraction of fluids utilizing a differential pressure responsive restriction at one point within the vacuum line of a collection system. No attempt is made at precise control or variation of the rate of fluid collection as taught by the cited reference. The present invention does not contemplate the control of the rate of delivery of a fluid to the body.
U.S. Pat. No. 3,763,862 discloses a vacuum collection system particularly applicable to multi-station dental apparatus. This reference discloses a displaceable diaphragm disposed to close the inlet upon manual movement of a control valve. The reference also discloses a valve in the inlet portion of the apparatus whereby the vacuum applied for collection is controlled by opening the inlet system through the valve to the atmosphere. In this reference the responsive diaphragm is in the inlet portion of the device, is responsive only to the position of a manually-controlled valve and acts solely as an on-off valve. The valve effecting the vacuum within the system is in the inlet portion of the system and merely degrades the vacuum by venting the inlet to the atmosphere.
U.S. Pat. Nos. 3,848,628 and 3,814,098 both disclose a fluid collection device comprising a flexible bag within a rigid container. Vacuum is applied to both sides of the flexible bag within the container to prevent its collapse due to differential pressures. There are provided slits in the bag that allow gas flow through the bag to aid the pressure equalization. In both references, the size of the orifices are determined by the gas flow rate which is in turn determined by the degree of vacuum applied to the system. Where the vacuum is high, the orifices enlarge to accommodate the larger gas flow through the system.
The size of the orifices of these cited references increase in cross section upon the application of increasing differential pressures.
The invention as disclosed in the illustrative embodiments herein provides an improved means of collecting non-gaseous fluids. By reducing the flow rate of gas through the system in response to increases in differential pressures across a variable flow restriction the invention desirably provides an increased rate of vacuum buildup when the inlet is partially or fully blocked while reducing the amount of gas ingested when the inlet is exposed to the atmosphere. In addition, the invention reduces the rate of exhaustion of gases from a cavity from which the non-gaseous fluid is being collected. In medical applications, the invention avoids air exhaustion from the lungs during trachea suctioning and minimizes tissue grab adjacent the inlet.